1. Field of the Invention
This invention relates to a liquid-filled vibration-proof device used for a body mount or a suspension support of a vehicle.
2. Description of Related Art
As a body mount used for a rear suspension of a vehicle or the like, such as an automotive vehicle, there is known a body mount that has an internal cylinder member connected and fixed to one of a vehicle body and a frame on the suspension side supporting the vehicle body, with its axial center oriented vertically. An external cylinder member is connected and fixed to the other around the internal cylinder member, and a rubber elastomer is arranged between and interconnects the internal and external cylinder members. In the rubber elastomer, there is provided an annular liquid chamber surrounding the internal cylinder member.
Also in a suspension support such as a strut mount, for example, a vibration-proof device as disclosed in JP Patent Publication 10-38014 (1998) A is proposed, wherein an internal cylinder member to be fitted to a top of a strut rod and an external cylinder member to be fitted to the vehicle body side are joined by a rubber elastomer disposed between both and further, the rubber elastomer is provided therein with an annular liquid chamber surrounding the internal cylinder member.
With the above-mentioned vibration-proof devices, like the body mount or suspension support, when a vibration load mainly in the axial direction is input, the vibration is adapted to be suppressed by the effect of lowering in dynamic spring constant by the liquid chamber thereby to obtain a required vibration-proof characteristic.
In either case of the vibration-proof devices mentioned above, for the vibrations in a frequency region lower than 150 Hz, the aforesaid lowering effect in dynamic spring constant by the liquid chamber is obtainable and a required vibration-proof characteristic can be exhibited. Notwithstanding this, for the vibrations in a high frequency spectrum of 150 Hz and upward, in particular, in the vicinity of 150xcx9c300 Hz the lowering effect of the dynamic spring constant is small and the vibration-suppressing effect is not sufficiently obtained. Further improvement over the vibration-proof devices of these types is therefore desired.
In view of the prior art situation above the present invention has been made and is contemplated solving the aforementioned problems by the provision of the vibration-proof device of this kind with a stirring member in the liquid chamber, accordingly.
The invention consists in a vibration-proof device comprising an internal cylinder member, an external cylinder disposed concentrically outwardly of the internal cylinder member, and a rubber elastomer disposed between the internal and the external cylinder members, the rubber elastomer having therein an annular liquid chamber surrounding the internal cylinder member; and the vibration-proof device is characterized in that inside the liquid chamber there is provided an annular stirring member projecting inwardly from an inner periphery side of the external cylinder member toward a chamber wall face on the internal cylinder member side so as to hold a clearance therebetween.
According to the vibration-proof device, the liquid chamber is divided by the stirring member into upper and lower parts, which are in communication through a narrow clearance between the stirring member and the chamber wall face on the internal cylinder member side. As a consequence, upon inputting of a vibration load, in particular, a vibration load in the vertical direction, the liquid in the liquid chamber flows through the narrow clearance upwardly and downwardly. Because of resonance action due to the liquid fluidization, the dynamic spring constant can be lowered in a high frequency spectrum in the vicinity of 150 to 300 Hz, as well and the suppression of vibrations can be effectively achieved. Thus it is possible to exhibit good vibration-proof characteristics in a wide range of frequency spectrum.
Further the abovementioned vibration-proof device may be constructed so that the rubber elastomer comprises a main rubber portion bonded by vulcanization to an outer periphery of the internal cylinder member and a diaphragm bonded by vulcanization to the inner periphery of the external cylinder member; a main outer cylinder bonded by vulcanization to an outer periphery of the main rubber portion is fitted hermetically inside the external cylinder member and at the same time, an inside-of-diaphragm cylinder bonded by vulcanization to an inner periphery of the diaphragm is fitted hermetically to the outer periphery of the internal cylinder member, whereby forming the liquid chamber between the main rubber portion and the diaphragm.
By this structure, the liquid chamber, in which liquid is sealed and which is capable of deforming by input of vibrations, can be provided within the rubber elastomer and its assembling and construction is facilitated.
The stirring member is preferably held and pinched at its outer peripheral margin between one end of the main outer cylinder and a step portion at the inner periphery of the external cylinder member. Because of the construction, upon assembling, the stirring member can be incorporated in place easily and securely by preliminarily setting it on the place of the step portion at the inner periphery of the external cylinder member. Further in case where the step portion at the inner periphery of the external cylinder member is formed on an inner periphery of a rubber layer vulcanization-bonded to the inner periphery of the external cylinder member, it is possible to hold and pinch the stirring member elastically, stably and hermetically and to exhibit its function satisfactorily.
The stirring member may comprise a ring-formed plate made of a rigid body and a rubber portion encrusting an inward marginal portion of the ring-formed plate in the liquid chamber. In the event that the stirring member abuts on the chamber wall face on the internal cylinder member side by the input of vibrations in a direction perpendicular to the axis, it is thereby possible to absorb the shock, thus suppressing the generation of a hitting sound.
Alternatively it is also possible to construct the vibration-proof device of this invention so that the rubber elastomer comprises a main rubber portion bonded by vulcanization to the outer circumference of the internal cylinder member and a diaphragm forming the liquid chamber between both; the external cylinder member has an outside-of-diaphragm cylinder, including a cylinder portion to which the diaphragm is bonded by vulcanization, to be fitted to a vehicle body panel, etc. and a main outer cylinder bonded by vulcanization to an outer periphery of the main rubber portion; the main outer cylinder is fitted hermetically, at its one end, to the inside of the cylinder portion of the outside-of-diaphragm cylinder and at the same time, an inside-of-diaphragm cylinder bonded by vulcanization to an inner periphery of the diaphragm is fitted hermetically to the outer periphery of the internal cylinder member, whereby forming the liquid chamber between the main rubber portion and the diaphragm.
By this construction, the liquid chamber sealed with liquid and capable of deforming by inputting of vibrations can be provided inside the rubber elastomer and its assembling and construction is also facilitated.
In this vibration-proof device as well, it is preferred that the stirring member be held and pinched at its outer marginal portion between one end of the main outer cylinder and a step portion at the inner periphery of the cylinder portion of the outside-of-diaphragm cylinder. In assembling, it is possible to incorporate easily the stirring member in place by setting it on a place of the step portion at the inner periphery of the external cylinder member. Further in case where the step portion at the inner periphery of the cylinder portion of the outside-of-diaphragm cylinder is formed on an inner periphery of a rubber layer bonded by vulcanization to the inner periphery of the cylinder portion, it is possible to hold and pinch the stirring member elastically, stably and hermetically.